The present invention relates to a vehicle having ground drive wheels which are hydrostatically driven, and more particularly relates to controls for a dual-path hydrostatic drive system.
U.S. Pat. No. 5,649,606 granted to Bebernes et al. on Jul. 22, 1997 discloses a dual-path hydrostatic drive system which is controlled by a steering and ground speed control mechanism including a steering rack in the form of a sector which is pivoted to opposite sides of a neutral position in response to steering wheel operation. This movement of the steering rack is transmitted to a first sprocket of a timing belt drive having a second sprocket joined to an output member that is linked with the hydrostatic transmission pump controllers.
This steering control is not entirely satisfactory due to the cost and complexity of the timing belt drive, the latter requiring the center distance between its input and output sprockets to be adjusted to maintain proper belt tension while at the same time maintaining proper alignment between the two sprockets.
According to the present invention there is provided a steering and ground speed control mechanism which represents an improvement over the control mechanism disclosed in U.S. Pat. No. 5,649,606.
A broad object of the invention is to provide a steering and ground speed control mechanism for a dual-path hydrostatic transmission, the mechanism including a quadrant-shaped steering rack but being more economical and less complex than the control mechanism disclosed in U.S. Pat. No. 5,649,606.
A more specific object of the invention is to provide a control mechanism as set forth in the immediately preceding object wherein a four-bar linkage is used for transmitting pivotal motion of the steering rack quadrant to the output plate that is linked to the hydrostatic transmission pump controllers.